As the result of trauma or lung disease, it occasionally becomes difficult for particular individuals to breathe without the assistance of a respirator or other mechanical apparatus which tends to force air into the lungs of an individual to assist or substitute for the normal inspiration (or inhalation). A respirator or other mechanical means is also generally used to extract air from the lungs of the individual, substituting for the normal expiration (or exhalation) portion of the respiration (or breathing) cycle.
A variety of devices are used to interconnect a respirator, or mechanical breathing means to the air passage of a patient. These devices typically include tubes which are positioned along the laryngotracheal airway between the mouth or nose and the lungs of the patient. A particular class of this type of tube is referred to as an endotracheal tube which is preferably routed through the mouth of a patient and oriented such that the opening of the tube within the body cavity is located immediately above the lungs of the patient.
Examples of this type of endotracheal tube include U.S. Pat. No. 4,334,534 issued to Ozaki in which an endotracheal tube having three internal tubes is inserted through the mouth of the patient and manipulated into the esophageal airway to allow it to be positioned and used for ventilation. The Ozaki device is intended for use as an emergency medical apparatus to be applied by a paramedic, emergency medical technician, or other emergency response personnel in emergency field applications. The Ozaki invention has an inflatable cuff which can be used to form a seal between the walls of the endotracheal tube and the trachea or esophagus depending on where the device is located when it is inserted into the patient. The Ozaki device can also be adapted for use in conjunction with a stomach drain tube to evacuate the contents of the stomach when the Ozaki device is appropriately positioned.
U.S. Pat. No. 4,519,388 issued to Schwanbom, et al. describes a respirator device which has one end located in the trachea of a patient, and is combined with the use of a venturi tube to alleviate problems caused by coughing spells and reduced barotraumas. Schwanbom maintains a continuous vacuum in order to accomplish these goals.
U.S. Pat. No. 4,646,733 issued to Stroh, et al. describes a flexible endotracheal tube through which a second tube can be inserted for directing respiratory air pulses into the trachea of the patient. Stroh employs either mechanical rotary slide valves or electrically operated valves in order to activate the device.
U.S. Pat. No. 4,850,371 issued to Broadhurst, et al. describes a device used to monitor the quantity and composition of inhaled and expired gases, and to calculate the pulmonary function and cardiac output based on the inhaled and expired gas composition. Broadhurst employs an endotracheal tube which incorporates a miniature mass spectrometer to continuously and rapidly measure the gas content. Broadhurst employs an endotracheal tube with several internal passage ways through which gas is sampled.
U.S. Pat. No. 4,573,462, issued to Baum, describes a respiratory system which incorporates a pressure relief valve. An endotracheal tube having a single tube is employed in Baum. The gas cycle to the patient is passed through a carbon dioxide absorber in order to purify the content of the air supplied to a patient.
U.S. Pat. No. 4,681,100, issued to Brychta, et al., employs an endotracheal tube having several different tubes contained within it in order to allow cleaning the air passages of a patient without interrupting ventilation. The Brychta invention can be used in conjunction with two ventilation generators to provide gas supplying having different over pressures.
U.S. Pat. No. 4,596,247, issued to Whitwam, et al., describes a respirator in which the gas inlet and gas outlet sections are spaced apart in the respirator. The respirator is then connected to a standard endotracheal tube which is inserted into a patient.
U.S. Pat. No. 4,291,691, issued to Cabal, et al., describes an adaptor which is inserted between a respirator and the artificial airway of a patient. The adaptor allows one or more additional tubes to be inserted through the main cavity of a single endotracheal tube without disturbing the seal of the main endotracheal tube.
U.S. Pat. No. 3,734,094, issued to Kolobow, describes a multipurpose esophageal instrument which can be used for suctioning out secretions from the stomach. The Kolobow device also includes a variety of electrodes located on the esophageal tube in order to sense the heart rate and provide an electrocardiogram (EKG) which is sensed from within the body cavity of the patient.
U.S. Pat. No. 4,383,534, issued to Peters, describes an endotracheal tube which is augmented with a temperature detector, electrocardiogram detector, and audio sensing means to monitor the sound of the heart and respiration. Blood pressure sensing means is also connected to the device.
There is typically a trade off between the diameter of the endotracheal tube and the operating pressure of the respirator. The larger the diameter of the endotracheal tube, the lower the required pressure in order to get the same volume of air forced into the lungs. The larger volume accommodated by a large diameter endotracheal tube results in a large volume of un-circulated or dead space gas located between the end of the endotracheal tube inserted into the body of the patient and the respirator. This dead space gas has a high carbon dioxide content, and is forced back into the lungs of the patient during the next inspiration cycle.
In order to reduce the volume of uncirculated or dead space gas contained within the endotracheal tube, a smaller diameter endotracheal tube may be employed. This results in a higher operating pressure of the endotracheal tube in order to force the same volume of air into the lungs of the patient during the same period of time allowed for the inspiration cycle. The higher operating pressure of this type of endotracheal tube requires the use of a diffuser, or other comparable apparatus near the endotracheal tube placed within the patient in order to prevent any damage to the airway, lungs, and the like, as a result of application of high pressure air or oxygen through the endotracheal tube. Whitwam, et al., discloses one approach in which high pressure air pulses are "chopped" and applied to the distal end of an endotracheal tube.
All of the aforementioned endotracheal tubes and monitoring devices employ at least one tube which is used to supply air to the lungs of a patient and withdraw air from the lungs of the patient. Intratracheal pulmonary ventilation(ITPV) developed by Kolobow at the National Institute of Health in Bethesda provides administration of humidified air or oxygen at a continuous flow rate through a catheter which is fed through the endotracheal tube using the apparatus of Cabal, or other suitable devive. This technique is described in:
1. Muller E, Kolobow T, Mandava S & al, Intratracheal Pulmonary Ventilation (ITPV). A new technique to ventilate lungs as small as 12% of normal. Pediatr Res 1991;29(4):326A.
2. Kolobow T, Muller E, Mandava S & al, Intratracheal Pulmonary Ventilation (ITPV). A new technique. Pediatr Res 1991; 29(4):31A.
3. Aprigliano M, Kolobow T, Rossi N & al, Intratracheal Pulmonary ventilation (ITPV) in the management of acute respiratory failure (ARF). Am Rev Resp Dis 1992;145(4):A455.
This ITPV catheter is inserted inside and along the endotracheal tube and its distal tip is positioned near the distal end of the endotracheal tube. The catheter is equipped with a gas flow diffuser at its distal end which is covered by a sleeve. This sleeve reverses the direction of gas flow after it exits the distal tip of the catheter, so that its final direction is away from the lungs. The result is continuous flushing and clearance of most of the un-circulated or dead space volume from carbon dioxide, and reduction in the amount of the gas that is recycled into the lungs during the next inhalation cycle.